The invention relates generally to power-driven conveyors and more particularly to conveyor belts having sets of stacks of rollers arranged to rotate in different directions to direct conveyed articles atop the rollers in different directions.
Conveyor belts sometimes include stacked pairs of rollers that are actively rotated to propel articles rearward along the conveyor belt. The roller at the bottom of the stack rolls on a bearing surface underlying the conveyor belt as the belt advances along a conveyor carryway. The forward rotation of the bottom roller contacting the top roller in the stack causes the top roller to rotate in the opposite direction to propel articles conveyed atop the top roller to be pushed rearward on the conveyor belt. The stacked pairs of rollers can also be used passively to help induct articles onto the conveyor belt from the side. In passive operation, the rollers are not actuated, but rotate freely to allow the momentum of an article to roll the freely rotatable rollers in a direction easing the article onto the conveyor belt.
Modular plastic conveyor belts with stacked rollers are especially useful in diverting articles across the conveyor on sharp trajectories. In modular plastic belts, such as INTRALOX® Series 400 Dual-Activated Roller belt, manufactured and sold by Intralox, L.L.C., Harahan, La., U.S.A., the stacks of rollers are mounted in cavities across each modular plastic belt row. The axes of rotation of all the rollers are parallel, so all articles are propelled in the same direction. So articles can be diverted off only one side of the belt and can be fed onto the belt from only one side. Furthermore, because each top roller is relatively short and does not extend beyond the confines of its belt row, gaps are formed between the top rollers at the hinge joints between consecutive belt rows. Articles with small footprints or bottom appendages can get caught in those gaps to tip over.